For a pretty salad, peel only half the cucumbers leaving strips of skin on each. Thinly slice cucumbers and onion. Mix and set aside in glass dish. Mix vinegar, water, and sugar and just bring to a boil. Pour over cucumber and onion mixture. Don't make the vinegar solution first and then chop the cucumber because it's important that the vinegar solution be hot to ensure proper flavoring. Add dill and stir. Refrigerate until cold or eat at room temperature.